LeetCode 356: Line Reflection Solution

Master LeetCode problem 356 (Line Reflection), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

356. Line Reflection

Medium

Array Hash Table Math

Problem Explanation

Explanation:

Given a list of points on a 2D plane, we need to determine if there exists a line such that the points can be reflected symmetrically about that line. To solve this problem, we can follow these steps:

Calculate the minimum and maximum x-coordinates of the points to find the axis of symmetry.
For each point, determine its reflection point on the axis of symmetry.
Check if the reflection point exists in the set of points.
If all points have valid reflection points, then return true; otherwise, return false.

Time complexity:

Calculating the min and max x-coordinates: O(n)
Creating a set of points: O(n)
Checking if all points have valid reflections: O(n) Overall time complexity: O(n)

Space complexity:

Storing the set of points: O(n)

Solution Code

import java.util.HashSet;

class Solution {
    public boolean isReflected(int[][] points) {
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        HashSet<String> set = new HashSet<>();

        for (int[] point : points) {
            min = Math.min(min, point[0]);
            max = Math.max(max, point[0]);
            set.add(point[0] + "," + point[1]);
        }

        int sum = min + max;
        for (int[] point : points) {
            int reflectedX = sum - point[0];
            if (!set.contains(reflectedX + "," + point[1])) {
                return false;
            }
        }

        return true;
    }
}

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